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Bug 1047022 - Remove manual addref for Session object. Let MediaRecorder hold reference to Session that makes a cycle reference, break it in DestrotedRunnable(). r=roc

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This commit is contained in:
Benjamin Chen 2014-08-18 11:42:49 +08:00
parent 9c29a00b4d
commit 2c2ddc25a7
2 changed files with 29 additions and 41 deletions
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66
content/media/MediaRecorder.cpp
View File

@ -70,10 +70,12 @@ NS_IMPL_RELEASE_INHERITED(MediaRecorder, DOMEventTargetHelper)
* Release session resource and remove associated streams from MSG.
*
* Lifetime of MediaRecorder and Session objects.
* 1) MediaRecorder creates a Session in MediaRecorder::Start function.
* And the Session registers itself to ShutdownObserver and also holds a
* MediaRecorder. Therefore, the reference dependency in gecko is:
* ShutdownObserver -> Session -> MediaRecorder
* 1) MediaRecorder creates a Session in MediaRecorder::Start function and holds
* a reference to Session. Then the Session registers itself to
* ShutdownObserver and also holds a reference to MediaRecorder.
* Therefore, the reference dependency in gecko is:
* ShutdownObserver -> Session <-> MediaRecorder, note that there is a cycle
* reference between Session and MediaRecorder.
* 2) A Session is destroyed in DestroyRunnable after MediaRecorder::Stop being called
* _and_ all encoded media data been passed to OnDataAvailable handler.
* 3) MediaRecorder::Stop is called by user or the document is going to
@ -150,18 +152,11 @@ class MediaRecorder::Session: public nsIObserver
class ExtractRunnable : public nsRunnable
{
public:
ExtractRunnable(already_AddRefed<Session>&& aSession)
ExtractRunnable(Session* aSession)
: mSession(aSession) {}
~ExtractRunnable()
{
if (mSession) {
NS_WARNING("~ExtractRunnable something wrong the mSession should null");
nsCOMPtr<nsIThread> mainThread = do_GetMainThread();
NS_WARN_IF_FALSE(mainThread, "Couldn't get the main thread!");
NS_ProxyRelease(mainThread, mSession);
}
}
{}
NS_IMETHODIMP Run()
{
@ -170,16 +165,15 @@ class MediaRecorder::Session: public nsIObserver
LOG(PR_LOG_DEBUG, ("Session.ExtractRunnable shutdown = %d", mSession->mEncoder->IsShutdown()));
if (!mSession->mEncoder->IsShutdown()) {
mSession->Extract(false);
nsRefPtr<nsIRunnable> event = new ExtractRunnable(mSession.forget());
nsRefPtr<nsIRunnable> event = new ExtractRunnable(mSession);
if (NS_FAILED(NS_DispatchToCurrentThread(event))) {
NS_WARNING("Failed to dispatch ExtractRunnable to encoder thread");
}
} else {
// Flush out remaining encoded data.
mSession->Extract(true);
// Destroy this Session object in main thread.
if (NS_FAILED(NS_DispatchToMainThread(
new DestroyRunnable(mSession.forget())))) {
new DestroyRunnable(mSession)))) {
MOZ_ASSERT(false, "NS_DispatchToMainThread DestroyRunnable failed");
}
}
@ -224,7 +218,7 @@ class MediaRecorder::Session: public nsIObserver
class DestroyRunnable : public nsRunnable
{
public:
DestroyRunnable(already_AddRefed<Session>&& aSession)
DestroyRunnable(Session* aSession)
: mSession(aSession) {}
NS_IMETHODIMP Run()
@ -246,8 +240,7 @@ class MediaRecorder::Session: public nsIObserver
ErrorResult result;
mSession->mStopIssued = true;
recorder->Stop(result);
if (NS_FAILED(NS_DispatchToMainThread(
new DestroyRunnable(mSession.forget())))) {
if (NS_FAILED(NS_DispatchToMainThread(new DestroyRunnable(mSession)))) {
MOZ_ASSERT(false, "NS_DispatchToMainThread failed");
}
return NS_OK;
@ -257,8 +250,7 @@ class MediaRecorder::Session: public nsIObserver
mSession->mMimeType = NS_LITERAL_STRING("");
recorder->SetMimeType(mSession->mMimeType);
recorder->DispatchSimpleEvent(NS_LITERAL_STRING("stop"));
recorder->RemoveSession(mSession);
mSession->mRecorder = nullptr;
mSession->BreakCycle();
return NS_OK;
}
@ -454,8 +446,7 @@ private:
// shutdown notification and stop Read Thread.
nsContentUtils::RegisterShutdownObserver(this);
already_AddRefed<Session> session(this); // addref in MediaRecorder::Start
nsRefPtr<nsIRunnable> event = new ExtractRunnable(Move(session));
nsRefPtr<nsIRunnable> event = new ExtractRunnable(this);
if (NS_FAILED(mReadThread->Dispatch(event, NS_DISPATCH_NORMAL))) {
NS_WARNING("Failed to dispatch ExtractRunnable at beginning");
}
@ -472,9 +463,7 @@ private:
if (NS_FAILED(NS_DispatchToMainThread(new PushBlobRunnable(this)))) {
MOZ_ASSERT(false, "NS_DispatchToMainThread PushBlobRunnable failed");
}
// Destroy this session object in main thread.
already_AddRefed<Session> session(this); // addref in MediaRecorder::Start
if (NS_FAILED(NS_DispatchToMainThread(new DestroyRunnable(Move(session))))) {
if (NS_FAILED(NS_DispatchToMainThread(new DestroyRunnable(this)))) {
MOZ_ASSERT(false, "NS_DispatchToMainThread DestroyRunnable failed");
}
}
@ -502,16 +491,23 @@ private:
mReadThread->Shutdown();
mReadThread = nullptr;
}
if (mRecorder) {
mRecorder->RemoveSession(this);
mRecorder = nullptr;
}
BreakCycle();
Stop();
}
return NS_OK;
}
// Break the cycle reference between Session and MediaRecorder.
void BreakCycle()
{
MOZ_ASSERT(NS_IsMainThread());
if (mRecorder) {
mRecorder->RemoveSession(this);
mRecorder = nullptr;
}
}
private:
// Hold reference to MediaRecoder that ensure MediaRecorder is alive
// if there is an active session. Access ONLY on main thread.
@ -640,16 +636,8 @@ MediaRecorder::Start(const Optional<int32_t>& aTimeSlice, ErrorResult& aResult)
mState = RecordingState::Recording;
// Start a session.
// Add session's reference here and pass to ExtractRunnable since the
// MediaRecorder doesn't hold any reference to Session. Also
// the DoSessionEndTask need this reference for DestroyRunnable.
// Note that the reference count is not balance here due to the
// DestroyRunnable will destroyed the last reference.
nsRefPtr<Session> session = new Session(this, timeSlice);
Session* rawPtr;
session.forget(&rawPtr);
mSessions.AppendElement();
mSessions.LastElement() = rawPtr;
mSessions.LastElement() = new Session(this, timeSlice);
mSessions.LastElement()->Start();
}

4
content/media/MediaRecorder.h
View File

@ -111,9 +111,9 @@ protected:
nsRefPtr<DOMMediaStream> mStream;
// The current state of the MediaRecorder object.
RecordingState mState;
// Hold the sessions pointer and clean it when the DestroyRunnable for a
// Hold the sessions reference and clean it when the DestroyRunnable for a
// session is running.
nsTArray<Session*> mSessions;
nsTArray<nsRefPtr<Session> > mSessions;
// It specifies the container format as well as the audio and video capture formats.
nsString mMimeType;